Inaccuracy of intraocular pressure measurement in congenital corneal opacity: three case reports.

BACKGROUND: To report three cases of congenital corneal opacity where intraocular pressure (IOP) readings were high despite the use of multiple anti-glaucoma eye drops and normalized after corneal transplantation. CASE PRESENTATION: Three Korean infants presented with bilateral dense stromal opacification which had been present since birth. IOPs measured by rebound tonometer were high despite administration of multiple anti-glaucoma medications. One eye of each patient underwent penetrating keratoplasty (PK) because corneal opacity impaired visual development. Immediately after PK, IOPs were normalized and maintained normal without medication, whereas they remained high in the contralateral unoperated eye. On histology, stromal fibrosis was observed in the removed corneal button, and molecular assays revealed increased levels of type 1 and 5 collagens. CONCLUSION: The IOP measurement using the conventional applanation-based tonometry can be inaccurate in congenital corneal opacity which is marked by corneal fibrosis. Therefore, IOP values should be interpreted with caution in these patients, and the possibility of false-positive diagnosis of glaucoma considered.

[Corneal Biomechanics and Measurement of Intraocular Pressure Measurement in Pathological Corneas]. / Biomechanik und Augeninnendruck bei Hornhauterkrankungen.

Measuring the intraocular pressure in eyes with corneal diseases or after corneal interventions often results in false values due to abnormal corneal biomechanics. Many different approaches are used to compensate for these abnormal corneal biomechanic properties, with varying measuring methods. There are differences when these alternative measuring methods are compared to the gold standard, applanation tonometry according to Goldmann. These differences vary between the methods and with different corneal changes. There is no clear recommendation on a precise method that is suitable for every pathological cornea. Therefore it is important to know the different variations and to include them in the analysis of every patient's intraocular pressure analysis.

Can Corneal Biomechanical Properties Explain Difference in Tonometric Measurement in Normal Eyes?

SIGNIFICANCE: Corneal biomechanical parameters can affect intraocular pressure (IOP) measurements by different tonometers compared with Goldmann applanation tonometer. This study implies that corneal hysteresis (CH) and corneal resistance factor (CRF) better explain variability in IOP measurements. PURPOSE: The aim of this study was to evaluate the effect of corneal properties on the difference in IOP measured by the Ocular Response Analyzer (ORA), Rebound Tonometer (RBT), Dynamic Contour Tonometer (DCT), and Tono-Pen from the Goldmann applanation tonometer (GAT). METHODS: An observational study was done on healthy participants in a tertiary eye care center. Corneal curvature was measured with a manual keratometer prior to IOP measurements. Intraocular pressure was measured by a single trained examiner with ORA, RBT, DCT, GAT, and Tono-Pen. CH and CRF were measured using the ORA. Central corneal thickness was measured using the ultrasonic pachymeter. Only the right eye was included for analysis. One-way analysis of variance was performed to compare variables, Bland-Altman plots to assess agreement, and regression analyses to study associated factors. RESULTS: We included 82 eyes of 82 participants with a mean age of 40.9 (14.3) years. Mean ± SD DCT IOP (15.22 ± 1.98) mmHg was significantly higher than GAT IOP (13.73 ± 2.42) (P = .01) and ORA Goldmann correlated IOP (13.66 ± 3.16) (P = .003). The limits of agreement between GAT and other tonometers measurements ranged between -5.0 and 2.1 mmHg. With multiple linear regression analyses, CH and CRF were found to be associated with the measured IOP differences between GAT and ORA (corneal compensated IOP and Goldmann correlated IOP) (P < .001) and DCT (P = .014, <.001) whereas differences between GAT and RBT measurements were independently explained by corneal curvature (P = .035) and central corneal thickness (P = .045). CONCLUSIONS: There was good agreement between GAT and other tonometers, but was not good enough for them to be used interchangeably. A combination of CH and CRF may better explain the variability between GAT and tonometers.

Assessing the True Intraocular Pressure in the Non-human Primate.

SIGNIFICANCE: For glaucoma patients, high intraocular pressure (IOP) is a risk factor for progressive neuropathy. Similarly, animal models used to study the disease are based on an experimental elevation of IOP. Thus, accurate IOP measurements are important in characterizing experimental models and resulting effects. PURPOSE: The purpose of the present study was to investigate IOP measurements in a non-human primate model of experimental glaucoma by comparing clinical tonometry (Tono-Pen and TonoVet) to the true IOP from intracameral manometry. METHODS: A total of 17 rhesus macaque eyes from 12 animals were used for this study. Eleven eyes had no previous experimental intervention, whereas six eyes were at varying stages of laser-induced experimental glaucoma. IOPs were adjusted by inserting a needle in the anterior chamber that was attached to a pressure transducer and syringe pump system. The anterior chamber IOP was adjusted to values between 10 and 50 mmHg and corresponding measures with Tono-Pen and TonoVet were taken. RESULTS: The IOPs by TonoVet and Tono-Pen were linearly related over the range of pressures tested (slope = 0.68 normal/healthy and 0.72 experimental glaucoma). For the most, TonoVet measures overestimated IOP at all anterior chamber pressure settings (mean difference of 3.17 mmHg, 95% CI 12.53 to -4.74 normal and 3.90 mmHg, 95% CI 12.90 to -6.53 experimental glaucoma). In contrast, Tono-Pen measures overestimated IOP at lower IOPs and underestimated at higher IOP (slope = -0.26 normal and -0.21 experimental glaucoma). CONCLUSIONS: The TonoVet and Tono-Pen tonometers that are often used to assess IOP in both clinical and experimental settings generally reflect the status of IOP, but the results from this study suggest that the instruments need calibration with true anterior chamber pressure for accurate measures in experimental models of glaucoma.

Tonometer validation and intraocular pressure reference values in the normal chinchilla (Chinchilla lanigera).

OBJECTIVES: To determine accuracy and precision of three commonly used tonometers (TonoVet® and TonoLab® (ICare Oy, Finland)-rebound tonometers, and Tono-Pen VET™ (Reichert, NY)-applanation tonometer) in normal chinchillas, and to establish a normal intraocular pressure (IOP) reference range in this species. METHODS: The anterior chambers of three chinchilla eyes were cannulated ex vivo and readings obtained at manometric IOPs from 5 to 80 mmHg, using each of the three tonometers in random order. Data were analyzed by linear regression, ANOVA, and Bland-Altman plots. Tonometry was performed in both eyes of 60 chinchillas (age 8 weeks-16.2 years) using the TonoVet® and relationship between age and IOP analyzed using linear regression. For all statistical tests, P < 0.05 was significant. RESULTS: Intraocular pressure values obtained using the Tono-Pen VET™ and TonoVet® (in dog calibration mode;'d') showed strong linear correlation with manometry within the physiologic and clinically relevant range of IOP (0-50 mmHg). The TonoVet® 'd' setting displayed significantly greater precision over the full range of IOP evaluated than the Tono-Pen VET™, and both TonoVet and Tono-Pen VET™ were significantly more accurate than the TonoLab® tonometer. Mean ± SD IOP (TonoVet® 'd') in chinchillas was 9.7 ± 2.5 mmHg, and the 95% reference interval was 4.7-14.7 mmHg. CONCLUSIONS: Both the Tono-Pen VET™ and TonoVet® provided clinically acceptable estimates of IOP in chinchillas. The TonoVet® provides accurate and precise IOP values, while Tono-Pen VET™ derived measurements showed greater variability. Values obtained either with the TonoLab® or TonoVet® used in the 'unspecified' calibration setting were inaccurate in this species.

Goldmann applanation tonometry error relative to true intracameral intraocular pressure in vitro and in vivo.

BACKGROUND: Goldmann applanation tonometry (GAT) error relative to intracameral intraocular pressure (IOP) has not been examined comparatively in both human cadaver eyes and in live human eyes. Futhermore, correlations to biomechanical corneal properties and positional changes have not been examined directly to intracameral IOP and GAT IOP. METHODS: Intracameral IOP was measured via pressure transducer on fifty-eight (58) eyes undergoing cataract surgery and the IOP was modulated manometrically on each patient alternately to 10, 20, and 40 mmHg. IOP was measured using a Perkins tonometer in the supine position on 58 eyes and upright on a subset of 8 eyes. Twenty one (21) fresh human cadaver globes were Intracamerally IOP adjusted and measured via pressure transducer. Intracameral IOP ranged between 5 and 60 mmHg. IOP was measured in the upright position with a Goldmann Applanation Tonometer (GAT) and supine position with a Perkins tonometer. Central corneal thickness (CCT) was also measured. RESULTS: The Goldmann-type tonometer error measured on live human eyes was 5.2 +/-1.6 mmHg lower than intracameral IOP in the upright position and 7.9 +/- 2.3 mmHg lower in the supine position (p < .05). CCT also indicated a sloped correlation to error (correlation coeff. = 0.18). Cadaver eye IOP measurements were 3.1+/-2.5 mmHg lower than intracameral IOP in the upright position and 5.4+/- 3.1 mmHg in the supine position (p < .05). CONCLUSION: Goldmann IOP measures significantly lower than true intracameral IOP by approximately 3 mmHg in vitro and 5 mmHg in vivo. The Goldmann IOP error is increased an additional 2.8 mmHg lower in the supine position. CCT appears to significantly affect the error by up to 4 mmHg over the sample size.

Comparison of intraocular pressure as measured by three different non-contact tonometers and goldmann applanation tonometer for non-glaucomatous subjects.

BACKGROUND: To compare the measurement of intraocular pressure (IOP) among the three different non-contact tonometers (NCT) and the Goldmann applanation tonometer (GAT) for non-glaucomatous subjects. METHODS: In 52 eyes of 52 non-glaucomatous subjects, IOP was measured sequentially with the Canon TX-20P, the Nidek NT-530P, the Topcon CT-1P, and the GAT at the same time. We evaluated the IOP-measurement agreement among the tonometers as well as the factors affecting the measurements. RESULTS: A significant positive correlation was shown between the IOP values obtained with GAT and each NCT. The Canon TX-20P showed statistically the most significant agreement with the GAT (ICC 0.906, 95% CI 0.837-0.946). In an analysis of the Bland-Altman plots, the Canon TX-20P also showed the largest mean bias (1.38 mmHg) but the narrowest limits of agreement (LoA) (95% LoA; ± 3.43 mmHg). The Topcon CT-1P showed the smallest mean bias (0.48 mmHg) but the widest LoA (95% LoA; ± 4.16 mmHg). The Topcon CT-1P and Nidek NT-530P both showed a significantly positive correlation between increasing central corneal thickness (CCT) and increasing IOP. CONCLUSION: There was a statistically significant correlation between each of the three different NCT and the GAT measurements. IOP measured with the Canon TX-20P and Topcon CT-1P tended to be higher, and with the Nidek NT-530P lower, than with the GAT. Practitioners need to know the properties of their own NCTs and their respective measurement tendencies.

Measurement of tear production and intraocular pressure in ducks and geese.

OBJECTIVES: The purpose of this study was to establish a reference value of tear production and intraocular pressure in clinically normal ducks and geese. ANIMAL STUDIED: The study population consisted of forty-eight ducks (24 males and 24 females) and fifty-two geese (26 males and 26 females). PROCEDURES: Birds were gently physically restrained in dorsoventral position without any pressure to the head and neck. Tear secretion and intraocular pressure were measured using 5-mm-wide Schirmer tear test strips and TonoVet® rebound tonometer, respectively. RESULTS: Overall mean ± 2SD STT and IOP values of all eyes were 6.2 ± 2.2 mm/min and 10.2 ± 2.2 mmHg, respectively, for the ducks; 5.5 ± 2.6 mm/min and 9.1 ± 2.0 mmHg, respectively, for the geese. There was no statistically significant difference in IOP between left eye and right eye or between males and females in ducks (P = 0.56, P = 0.63) and geese (P = 0.23, P = 0.22). Analysis of variance revealed that there were no significant differences in the STT and IOP between the breeds in ducks (P = 0.49, P = 0.68) and geese (P = 0.14, P = 0.26). CONCLUSIONS: Results of this study may be beneficial for the diagnosis and therapeutic monitoring of ducks and geese affected with Keratoconjunctivitis sicca, glaucoma, and uveitis.

Research: Validity of Measurements when Reusing Icare Probes.

BACKGROUND: It has been reported that reusing Icare tonometer probes may not pose a considerable risk of transmission of infection, thereby supporting this practice under extraordinary circumstances, such as mass glaucoma screenings in developing countries. The present study sought to determine whether reusing the probes reduced the validity of pressure readings. METHODS: Thousands of measurements were made with the same Icare probe on a purpose-built calibration device. A second set of measurements was made during which the Icare probe head was wiped with an alcohol pad between each reading. RESULTS: Statistically different readings were observed between the no-wipe and wipe groups for most of the settings evaluated. In addition, statistically significant readings were noted for a few of the settings as the number of readings increased for either group. However, these differences would not be considered clinically significant. CONCLUSION: This study suggests that reusing Icare tonometer probes, even for hundreds of measurements, would not reduce the clinical utility of the pressure readings. For mass screenings in developing countries where cost savings is crucial, considering the reuse of Icare tonometer probes seems reasonable.

Comparisons of the Tono-Pen® and Goldmann Applanation Tonometer in the Measurement of Intraocular Pressure of Primary Open Angle Glaucoma Patients in a Hospital Population in Southwest Nigeria.

OBJECTIVE: The aim of this study was to compare intraocular pressure (IOP) measured with the Tono-Pen® to that measured using the Goldmann applanation tonometer (GAT) in patients with primary open angle glaucoma attending a glaucoma clinic. SUBJECTS AND METHODS: A comparative clinic-based observational study was conducted involving 75 patients (39 men and 36 women) attending a glaucoma clinic in Southwest Nigeria. A pretested structured questionnaire was used to collect sociodemographic data. The Tono-Pen and the GAT were used to measure the IOP in each patient. Central corneal thickness (CCT) was measured with an ultrasonic pachymeter, and the corrected GAT value was calculated for each patient. The Tono-Pen readings were compared with the uncorrected and corrected GAT readings. Descriptive and comparative analyses were performed. Values for p < 0.05 were considered statistically significant. RESULTS: The mean age of the participants was 60.39 ± 16.71 years. The mean IOP using the Tono-Pen was 21.1 ± 6.8 mm Hg versus the mean uncorrected GAT value of 17.1 ± 6.9 mm Hg and the corrected GAT value of 18.9 ± 7.5 mm Hg. The mean CCT was 510.5 ± 29.6 µm. The mean differences between the Tono-Pen reading and uncorrected and corrected GAT readings were 3.9 ± 2.6 and 2.1 ± 3.5 mm Hg, respectively. Gender (Tono-Pen vs. GAT; p = 0.981 vs. 0.437) and corneal thickness (p = 0.057) did not significantly affect the IOP value. Of the 75 patients, 68 (90.7%) preferred the Tono-Pen to the GAT. CONCLUSION: In this study, the Tono-Pen gave a higher value for IOP than the uncorrected and corrected GAT values. Gender and corneal thickness did not significantly affect the measurements. Most patients found the Tono-Pen more acceptable than the GAT.

Agreement between diurnal variations of intraocular pressure by Tono-Pen and Goldmann applanation tonometer in patients on topical anti-glaucoma medication.

To estimate agreement in diurnal variations of intraocular pressure (IOP) by Tono-Pen (TP) and Goldmann applanation tonometer (GAT) in glaucoma patients on topical anti-glaucoma medication(s). IOP was measured at every 3 h from 7 a.m. to 10 a.m. in 50 eyes of glaucoma patients on topical medication(s). Diurnal fluctuation of IOP by each method was calculated as maximum-minimum IOP in a day. Central corneal thickness (CCT) was measured by ultrasonic pachymeter. There was good correlation between TP and GAT at all times during a day, minimum, and maximum IOPs during a day (Correlation coefficient, 0.706 at 7 a.m., 0.624 at 10 a.m., 0.682 at 1 p.m., 0.814 at 4 p.m., 0.652 at 7 p.m., 0.572 at 10 p.m., 0.668 minimum IOP, 0.689 maximum IOP). Mean IOPs by TP were always higher than GAT at all times during a day. Bland-Altman plots suggested a close relationship between the two sets of readings, and that this relationship was consistent at different times in a day, in maximum IOPs, minimum IOPs and also in fluctuation of IOPs. Linear regression analysis between the differences of diurnal fluctuation (diurnal fluctuation by GAT-diurnal fluctuation by TP) and CCT showed strong association (R 2 = 0.857, p < 0.001). The mean change in difference of diurnal fluctuation (GAT-TP) for a 10-micron increase in CCT was 0.69 mmHg. TP can be considered a reliable alternative to GAT in glaucoma patients for knowing the diurnal control of IOP; however these two methods should not be used interchangeably. Difference of diurnal fluctuation between two methods is dependent on CCT.

Repeatability and reproducibility of applanation resonance tonometry: a cross-sectional study.

BACKGROUND: To assess repeatability (intra-observer variability) and reproducibility (inter-operator variability) of intraocular pressure (IOP) measurements with servo-controlled Bioresonator Applanation Resonance Tonometry (ART) and to evaluate possible influential factors. METHODS: The study included 178 patients (115 glaucoma and 63 controls; one eye per subject). IOP was measured once with a Goldmann applanation tonometer (GAT) and twice by ART (ART1, ART2), in randomized sequence, by a single operator to assess intra-operator variability. Each ART measurement consisted on 3 readings. To assess inter-operator variability 2 evaluators performed 2 measurements each (in random order) on the same patient. Repeatability and reproducibility were assessed by the coefficient of variation (CoV) and intraclass correlation coefficient (ICC). RESULTS: In the entire cohort, ART1 was 0.4 ± 2.2 mmHg (-7.0 to 5.7 mmHg) higher than ART2 (p = 0.03) regardless of test order. Intra-operator CoV was 7.0% ± 6.3%, and ICC was 0.80-0.92. Inter-operator CoV ranged between 5.7% ± 6.1% and 8.2% ± 7.2%, and ICC between 0.86 and 0.97. ART1 and 2 were respectively 1.7 ± 3.1 and 1.3 ± 3.1 mmHg higher than GAT (p < 0.01). Test-retest difference with ART fell within ±1 mmHg in 41% of cases, within ±2 mmHg in 70%, within ±3 mmHg in 85%. 15% had a test-retest difference higher than ± 3 mmHg; Bland-Altman 95% intervals of confidence were -3.9 and +4.6 mmHg. Results were unaffected by age, diagnosis, central corneal thickness, keratometry, operator, randomization sequence. CONCLUSIONS: In most cases ART repeatability and reproducibility were high, with no differences due to patients' characteristics. ART measurements overestimated GAT by a mean of 1.3-1.7 mmHg.

Conjunctival flora, Schirmer's tear test, intraocular pressure, and conjunctival cytology in neotropical primates from Salvador, Brazil.

BACKGROUND: This study aimed to establish reference values for selected ophthalmic diagnostic tests in healthy neotropical primates from Salvador, Brazil. METHODS: A total of 73 intact adults, including Callithrix jacchus (n = 31), Callithrix penicillata (n = 8), Cebus sp. (n = 22), and Cebus xanthosternos (n = 9) were used to evaluate the normal conjunctival bacterial flora. Cebus xanthosternos (n = 12) were used to evaluate tear production with Schirmer's tear test (STT), intraocular pressure (IOP), and conjunctival cytology. RESULTS: For all animals evaluated, Gram-positive bacteria were predominant. Results of the diagnostic tests in Cebus xanthosternos were as follows: STT: 14.92 ± 5.46 mm/minutes, IOP: 19.62 ± 4.57 mmHg, and conjunctival cytology revealed intermediate squamous epithelial cells in great quantities. CONCLUSIONS: These ophthalmic reference values will be particularly useful to diagnose discrete or unusual pathological changes in the neotropical primates eye.

Repeatability of intraocular pressure measurements with Icare PRO rebound, Tono-Pen AVIA, and Goldmann tonometers in sitting and reclining positions.

BACKGROUND: Icare PRO (ICP) is a new Rebound tonometer that is able to measure intraocular pressure (IOP) in both sitting and reclining positions. In this study, the gold standard Goldmann tonometer (GAT) was compared to ICP and Tono-Pen AVIA (TPA). Hypothesis was that repeatability of GAT is superior to ICP and TPA. METHODS: 36 eyes of 36 healthy caucasian individuals, 13 male and 26 females, 17 right and 19 left eyes have been included in this prospective, randomized, cross-sectional study. The study was conducted at a single site (Dept. of Ophthalmology, University Hospital Zurich, Switzerland). Primary outcome measures were Intraclass correlation coefficients (ICC) and coefficients of variation (COV) and test-retest repeatability as visualized by Bland-Altman analysis. Secondary outcome measures were IOP in sitting (GAT, ICP and TPA) and in reclining (ICP and TPA) position. RESULTS: Mean IOP measured by GAT was 14.9 ± 3.5 mmHg. Mean IOP measured by ICP was 15.6 ± 3.1 mmHg (with TPA 14.8 ± 2.7 mmHg) in sitting and 16.5 ± 3.5 mmHg (with TPA 17.0 ± 3.0 mmHg) in reclining positions. COVs ranged from 2.9% (GAT) to 6.9% (ICP reclining) and ICCs from 0.819 (ICP reclining) to 0.972 (GAT). CONCLUSIONS: Repeatability is good with all three devices. GAT has higher repeatability compared to the two tested hand-held devices with lowest COVs and highest ICCs. IOP was higher in the reclining compared to the sitting position. TRIAL REGISTRATION: The study was registered to the Clinical Trials Register of the US National Institute of Health, NCT01325324.

The accuracy of dynamic contour tonometry over soft contact lenses.

PURPOSE: Dynamic contour tonometry (DCT) has been shown to measure the intraocular pressure (IOP) independently of corneal thickness. This study aimed to investigate if DCT remains accurate when the IOP measurement is taken over soft contact lenses (CLs) of different thicknesses and material characteristics. METHODS: This was a prospective clinical study that included 42 patients. Subject age was 22 to 59 years (26.5 ± 6.3 years). Intraocular pressure and ocular pulse amplitude (OPA) measurements were taken under topical anesthesia without CLs and over various daily disposable CLs with -0.50, +5.00, and -5.00 diopters (D) in hydrogel (Nelfilcon A) and in silicone hydrogel (Narafilcon A) materials. RESULTS: No statistically significant differences were found when comparing the IOP measurements obtained using either of the different CL powers of -0.50 or -5.00 D, irrespective of which CL material was being used. However, the difference of 0.62 mm Hg observed when the Nelfilcon A with a power of +5.00 D was used turned out to be highly statistically significant (p = 0.0002), whereas the Narafilcon A with the same power of +5.00 D, with a small difference of -0.16 mm Hg, was not. Regarding OPA measurements, no significant differences were found between measurements with and without CL neither for different materials nor for change in dioptrical power (F = 0, p = 1.000). CONCLUSIONS: This study showed good reliability of IOP and OPA measurements over CLs with varying thickness profiles and different soft materials when using the DCT. Only a small but statistically significant difference of 0.62 mm Hg was found for the IOP measurement with the hydrogel CL of +5.00 D compared with "no CL."

The range of the waveform score of the ocular response analyzer (ora) in healthy subjects.

PURPOSE: The waveform score (WS) indicates the reliability of each intraocular pressure (lOP) measurement signal performed with the Ocular Response Analyzer (ORA, Reichert). We aimed to assess i) the range of waveform score in IOP measurements with ORA in healthy subjects and to ii) identify a cut-off WS value under which an ORA measurement should be discarded. METHODS: Prospective study including three ORA IOP measurements performed in the right eye of 80 healthy normal subjects. The different WS were recorded and the highest WS of the three measurements was analysed. ANOVA test was used to assess variance in repeated measurements. RESULTS: Mean age of 80 subjects was 46.7+/-15.6 years. Mean WS of the first IOP measurement was 4.8+/-2.0 and 4.8+/-1.7 and 5.0+/-1.9 respectively for the second and third measurements (p= 0.74). Mean WS of the analysed 240 signals (3 measurements per eye) was 4.9+/-1.9 (range: 1.2-9.5). The mean value of all the highest values per eye was 6.2+/-1.8 (range: 2.9 -9.5 and was significantly higher than the mean WS of the 240 signals together (p <0.001). The 10th percentile of all the best values was 3.7 and the 75th percentile 7.5. CONCLUSION: ORA measurements with WS <3.7 should be discarded in healthy normal subjects. As much as that the corresponding quality of the waveform ORA scan is satisfying, one single measurement with a WS >7.5 could be considered as sufficient. If this score cannot be reached after three consecutive measurements, the signal with the highest WS should be selected.

Treatment with recombinant human growth hormone during childhood is associated with increased intraocular pressure.

OBJECTIVE: To evaluate the association between recombinant human growth hormone (rhGH) treatment and intraocular pressure (IOP) in children. STUDY DESIGN: This is an observational cohort study including comparison between children treated with rhGH for at least 12 months (treatment group), matched children prior to treatment (control group), and population age-adjusted normograms of IOP. All children underwent an ocular slit lamp assessment and Goldmann applanation tonometry. Charts were reviewed for cause of therapy, peak stimulated growth hormone level prior to therapy, treatment duration, insulin-like growth factor 1, and rhGH dosage. RESULTS: The treatment group included 55 children and the control group included 24 children. Mean age at examination was comparable at 11.4 ± 3.3 years and 10.3 ± 2.6 years, respectively (P = .13). Mean treatment duration was 37.5 ± 22.8 months and mean rhGH dose was 0.04 ± 0.01 mg/kg/d. Mean IOP was significantly increased in the treatment group compared with the control group and compared with age-matched normograms (16.09 ± 2.2 mm Hg, 13.26 ± 1.83 mm Hg and 14.6 ± 1.97 mm Hg, respectively, P < .001). IOP was positively correlated with treatment duration (r = 0.559, P < .001) and rhGH dosage (r = 0.274, P = .043). CONCLUSION: IOP in children treated with rhGH is increased compared with a similar population without treatment and compared with healthy population normograms. IOP is associated with longer treatment duration and higher dosages.

Influence of central corneal thickness on measured intraocular pressure differentials: Nidek RKT-7700, Topcon CT-80 NCTs and Goldmann Tonometer.

PURPOSE: We sought to compare the intraocular pressure (IOP) measured by RKT-7700 and CT-80 noncontact tonometers (NCTs) with that measured by Goldmann applanation tonometry (GAT). We also examined the influence of central corneal thickness (CCT) on the agreement between both NCTs and GAT in a sub-population of healthy, young normals. METHODS: Triplicate IOP and CCT measurements were obtained twice from one randomized eye of 49 subjects (28 males and 21 females) aged 22.2 ± 1.3 (mean ± S.D.) years. Goldmann tonometry was performed subsequent to assessment with the RKT-7700 and CT-80, to negate the 'ocular massage effect', followed by ultrasound pachymetry. The results from each method were compared and assessed for repeatability and between-observer reproducibility. Analysis was performed to determine the correlation between the differences in IOP measurements and corneal thicknesses. RESULTS: The mean differences (±S.D.) in sessions 1 and 2 respectively between RKT-7700 and GAT (2.6 ± 2.0 and 2.7 ± 1.4 mmHg), between CT-80 and GAT (2.8 ± 2.0 and 3.2 ± 1.3 mmHg) were statistically significant (p < 0.0001). The repeatability coefficients in sessions 1 and 2 respectively were; ±1.2 and ±1.0 mmHg (GAT), ±1.3  and ±1.6 mmHg (CT-80), ±2.3  and ±1.7 mmHg (RKT-7700) and inter-observer reproducibility was; ±1.9 (RKT-7700), ±2.3 (GAT) and ±2.6 mmHg (CT-80). Between the corneal thickness and the differences in GAT-measured and NCT-measured IOPs, there was a significant negative correlation and a trend for a larger difference in thicker corneas. CONCLUSION: Neither the RKT-7700 nor the CT-80 can be used interchangeably with the Goldmann tonometer, although all three tonometers give repeatable measurements of IOP, in this sub-population. IOP differences between GAT and the NCTs significantly correlated with CCT, with the possibility of even greater differences in thicker corneas.

Comparative evaluation of Diaton and Goldmann applanation tonometers.

AIM: To evaluate the agreement between intra-ocular pressure (IOP) measurements with the Diaton and the Goldmann applanation tonometers (GAT). METHODS: In this cross-sectional observational study, a total of 196 eyes of 196 participants (66 patients with glaucoma, 130 healthy subjects) were included. IOP measurements were obtained from all patients using the Diaton and GAT. RESULTS: The average age of the patients enrolled in this study was 48.3 ± 14.6 years (range 18-79). The overall mean IOP measured by the Diaton was 17.2 ± 6.4 mm Hg, while that in glaucoma patients was 17.9 ± 6.2 mm Hg and in the control group 15.8 ± 4.9 mm Hg. Pearson's correlation coefficient showed a moderate correlation in IOP measurements by the two instruments in healthy controls (r = 0.460, p < 0.01); however, the same correlation for the glaucomatous subjects was noted to be poor (r = 0.261, p = 0.57). The limits of agreement (95% confidence intervals) ranged from -9.9 to +11.2 and from -15.3 to +19.7 mm Hg in healthy controls and glaucoma patients, respectively. CONCLUSION: The Diaton measurements do not correlate well with those provided by applanation tonometry. The two tonometers show very wide limits of agreement so they may not be used interchangeably in clinical practice for the measurement of IOP.

Tonopen XL assessment of intraocular pressure through silicone hydrogel contact lenses.

OBJECTIVES: To assess the accuracy of Tonopen XL measurement of intraocular pressure (IOP) through low-power (-0.25 to -3.00) and high power (-3.25 to -6.00) silicone hydrogel lenses of 3 different materials (galyfilcon A, senofilcon A, and lotrafilcon B). METHODS: Seventy-eight patients were recruited for participation in this study. All were habitual wearers of silicone hydrogel contact lenses, and none had been diagnosed with glaucoma, ocular hypertension, or anterior surface disease. IOP was measured with and without lenses in place in the right eye only. Patients were randomized to initial measurement either with or without the lens in place. A single examiner collected all data. RESULTS: No statistically significant differences were noted between IOP measured without lenses and IOP measured through low-power lotrafilcon B lenses or high-power or low-power galyfilcon A and senofilcon A lenses. However, we did find a statistically significant difference between IOP measured without lenses and IOP measured through high-power lotrafilcon B lenses. CONCLUSION: In general, Tonopen XL measurement of IOP through silicone hydrogel lenses may be sufficiently accurate for clinical purposes. However, Tonopen XL may overestimate IOP if performed through a silicone hydrogel lens of relatively high modulus.